How does diet influence stroke risk?
Different types of food are linked to risks of different types of stroke, according to a study published in the European Heart Journal. The study authors say the associations they found between different foods and different strokes might be explained partly by the effects on blood pressure and cholesterol.
Stroke is the second-leading cause of deaths worldwide, and comes in two different forms. Ischaemic stroke occurs when a blood clot blocks an artery supplying blood to the brain or forms somewhere else in the body and travels to the brain where it blocks blood flow, whereas haemorrhagic stroke occurs when there is bleeding in the brain that damages nearby cells. About 85% of strokes are ischaemic and 15% are haemorrhagic.
Until now, most studies have looked at the association between food and total stroke (all types of stroke combined), or focused on ischaemic stroke only. The European Prospective Investigation into Cancer and Nutrition (EPIC) study of more than 418,000 people in nine European countries, conducted between 1992 and 2000, investigated ischaemic stroke and haemorrhagic stroke separately.
The total amount of fibre (including fibre from fruit, vegetables, cereal, legumes, nuts and seeds) that people ate was associated with the greatest potential reduction in the risk of ischaemic stroke. Every 10 g more intake of fibre a day was associated with a 23% lower risk, which is equivalent to around two fewer cases per 1000 of the population over 10 years. The European Society of Cardiology (ESC) suggests people should consume 30–45 g of fibre a day, with good sources including wholemeal toast (6.6 g for two thick slices), broccoli (3 g for eight florets) and apples (1.2 g for one raw, unpeeled fruit).
Fruit and vegetables alone were associated with a 13% lower risk of ischaemic stroke for every 200 g eaten a day, which is equivalent to one less case per 1000 of the population over 10 years. The ESC and the World Health Organization Regional Office for Europe recommend consuming at least 400 g of fruit and vegetables a day.
But while higher intakes of fruit, vegetables, fibre, milk, cheese or yoghurt were each linked to a lower risk of ischaemic stroke, there was no significant association with a lower risk of haemorrhagic stroke. Meanwhile, greater consumption of eggs was associated with a higher risk of haemorrhagic stroke; for every 20 g of eggs consumed a day, there was a 25% higher risk of haemorrhagic stroke, or 0.66 extra cases per 1000 of the population over 10 years. A typical large-sized egg weighs approximately 60 g.
“The most important finding is that higher consumption of both dietary fibre and fruit and vegetables was strongly associated with lower risks of ischaemic stroke, which supports current European guidelines,” said first author Dr Tammy Tong, from the University of Oxford. “The general public should be recommended to increase their fibre and fruit and vegetable consumption, if they are not already meeting these guidelines.
“Our study also highlights the importance of examining stroke subtypes separately, as the dietary associations differ for ischaemic and haemorrhagic stroke, and is consistent with other evidence, which shows that other risk factors, such as cholesterol levels or obesity, also influence the two stroke subtypes differently.”
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